Field of the Invention
The present disclosure relates to a touch sensor integrated type display device, and more specifically, to a touch sensor integrated type display device capable of preventing generation of a defective image between touch/common electrodes.
Discussion of the Related Art
Flat panel displays (hereinafter referred to as “display devices”), which are able to be manufactured as a large-sized display device at a low price and excellent in display quality (including motion picture representation, resolution, brightness, contrast ratio, color representation, etc.), has been recently developed in accordance with the need for display devices capable of properly displaying multimedia together with the development of multimedia. Various input devices, such as a keyboard, a mouse, a track ball, a joystick, and a digitizer, have been used in the display devices to allow users to interface with the display devices.
However, when the user makes use of these input devices, the user's dissatisfaction increases because the user is required to learn how to use the input devices and the input devices occupy space, thereby having difficulty in increasing the perfection of products. Thus, a demand for a convenient and simple input device for the display device capable of reducing erroneous operations is increasing. In response to the increased demand, a touch sensor has been proposed to recognize information when the user inputs information by directly touching the screen or approaching the screen with his or her hand or a pen while he or she watches the display device.
The touch sensor has a simple configuration capable of reducing the erroneous operations. The user can also perform an input action without using a separate input device and can quickly and easily manipulate a display device through the contents displayed on the screen. Thus, the touch sensor has been applied to various display devices.
The touch sensor used in display devices may be classified into an add-on type touch sensor, an on-cell type touch sensor, and an integrated type (or in-cell type) touch sensor depending on its structure. The add-on type touch sensor is configured such that the display device and a touch sensor module including the touch sensor are individually manufactured and then the touch sensor module is attached to an upper substrate of the display device. The on-cell type touch sensor is configured such that elements constituting the touch sensor are directly formed on the surface of an upper glass substrate of the display device. The integrated type touch sensor is configured such that elements constituting the touch sensor are mounted inside the display device to thereby achieve a thin profile and increase the durability of the display device.
Among the above touch sensors, a thickness of the display device is decreased as compared to the other touch sensors because the integrated type touch sensor may commonly use a common electrode of the display device as a touch/common electrode. Further, since the touch elements of the in-cell type touch sensor are formed inside the display device, the durability of the display device may increase. Hence, the in-cell type touch sensor has been widely used.
The integrated type touch sensor can solve the problems generated in the add-on type touch sensor and the on-cell type touch sensor because of the advantages of the thin profile and the durability improvement. The integrated type touch sensor may be divided into a light type touch sensor and a capacitive touch sensor depending on a method for sensing a touched portion. The capacitive touch sensor may be subdivided into a self-capacitive touch sensor and a mutual capacitive touch sensor.
The self-capacitive touch sensor forms a plurality of independent patterns in a touch area of a touch sensing panel and measures changes in capacitance of each independent pattern, thereby deciding whether or not a touch operation is performed. The mutual capacitive touch sensor crosses X-axis electrode lines (for example, driving electrode lines) and Y-axis electrode lines (for example, sensing electrode lines) in a touch/common electrode formation area of a touch sensing panel to form a matrix, applies a driving pulse to the X-axis electrode lines, and senses changes in voltages generated in sensing nodes defined as crossings of the X-axis electrode lines and the Y-axis electrode lines through the Y-axis electrode lines, thereby deciding whether or not a touch operation is performed.
In the mutual capacitive touch sensor, a mutual capacitance generated in touch recognition of the mutual capacitive touch sensor is very small, but a parasitic capacitance between gate line and data lines constituting the display device is very large. Therefore, it is difficult to accurately recognize a touch position because of the parasitic capacitance.
Further, the mutual capacitive touch sensor requires a very complex wiring structure because a plurality of touch driving lines for a touch drive and a plurality of touch sensing lines for a touch sensing have to be formed on the common electrode for multi-touch recognition.
On the other hand, because the self-capacitive touch sensor has a simpler wiring structure than the mutual capacitive touch sensor, touch accuracy may increase. Hence, the self-capacitive touch sensor has been widely used, if necessary or desired.
A related art liquid crystal display (hereinafter referred to as “touch sensor integrated type display device”), in which a self-capacitive touch sensor is integrated, is described below with reference to FIGS. 1 to 5.
FIG. 1 is a plan view schematically illustrating a related art touch sensor integrated type display device. FIG. 2 is a plan view of a portion A1 shown in FIG. 1, and FIG. 3 is a plan view of a portion A2 shown in FIG. 2. FIG. 4 is a cross-sectional view taken along line I-I′ shown in FIG. 3. FIG. 5 is a waveform diagram illustrating a ripple voltage generated in a touch/common electrode due to a gate signal applied to a gate line in a related art touch sensor integrated type display device.
Referring to FIG. 1, a touch sensor integrated type display device includes an active area AA, in which touch/common electrodes and pixel electrodes are disposed and data is displayed, and a bezel area BA disposed outside the active area AA. In the bezel area BA, various wires and driver integrated circuits (ICs) are disposed.
The active area AA includes a plurality of touch/common electrodes C11 to Cki disposed in a first direction (for example, x-axis direction) and a second direction (for example, y-axis direction) crossing the first direction and a plurality of touch/common lines L11 to Lki, that are arranged in parallel with one another in the second direction to connect the plurality of touch/common electrodes C11 to Cki to driver ICs IC1 to ICi.
The plurality of touch/common electrodes C11 to Cki disposed in the active area AA are formed by dividing a common electrode of a related art display device into multiple touch electrodes. The plurality of touch/common electrodes C11 to Cki operate as common electrodes in a display mode for displaying data and operate as touch electrodes in a touch mode for recognizing a touch location.
Referring to FIGS. 2 to 4, in the related art touch sensor integrated type display device, a plurality of pixel electrodes P correspond to one touch/common electrode. In an example of FIG. 2, twelve pixel electrodes P disposed in two rows and six columns are disposed to correspond to each of touch/common electrodes C11, C21, and C31.
The pixel electrodes P are respectively disposed in areas defined by gate lines G1 to G6 and data lines D1 to D6.
The pixel electrodes P are connected to the data lines D1 to D6 through thin film transistors and receive data voltages synchronized with gate signals supplied from the gate lines G1 to G6.
The touch/common electrodes C11, C21, and C31 receive a common voltage through touch/common lines L11, L21, and L31 in a display driving period and receive a touch driving voltage in a touch driving period. During the touch driving period, the touch/common lines L11, L21, and L31 supply a touch sensing voltage sensed by the touch/common electrodes C11, C21, and C31 to the driver ICs. The driver ICs determine a touch/non-touch operation and a touch location using a known touch algorithm.
The gate lines G1 to G6 and a gate electrode GE of a thin film transistor TFT are disposed on a substrate SUB.
The thin film transistor TFT includes the gate electrode GE extended from a gate line GL on the substrate SUB, a semiconductor active layer A that is disposed on a gate insulating layer GI covering the gate line GL and the gate electrode GE and partially overlaps the gate electrode GE, and a source electrode SE and a drain electrode DE are formed on the semiconductor active layer A and spaced apart from each other by a predetermined distance.
The data line D1 is disposed on the same layer as the source electrode SE and the drain electrode DE and is connected to the source electrode SE and spaced apart from the drain electrode DE.
The pixel electrode P is formed on the gate insulating layer GI and the drain electrode DE and is directly connected to the drain electrode DE.
The data line DL, the source electrode SE and the drain electrode DE of the thin film transistor TFT, and the pixel electrode P are covered with a first insulating layer INS1. The touch/common line L11 is formed on the first insulating layer INS1 and overlaps the data line D1. The touch/common line L11 on the first insulating layer INS1 is covered with a second insulating layer INS2.
The touch/common electrode C11 is disposed on the second insulating layer INS2 and overlaps the pixel electrodes P. The touch/common electrode C11 includes a plurality of slits SL, so as to form a horizontal electric field together with the pixel electrodes P. The touch/common electrode C11 is connected to the touch/common line L11 exposed through a contact hole CH passing through the second insulating layer INS2.
In the above-described touch sensor integrated type display device according to the related art, the touch/common electrode C11 is not disposed at a formation location of the thin film transistor TFT, in order to prevent the generation of parasitic capacitance. Namely, the touch/common electrode C11 is disposed not to overlap the thin film transistor TFT. Thus, a second gate line G2 is disposed between the touch/common electrodes C11 and C21, which are adjacent to each other in a vertical direction.
According to the above-described configuration of the related art touch sensor integrated type display device, the first gate line G1 is disposed to overlap the first touch/common electrode C11, but the second gate line G2 is disposed not to overlap the first touch/common electrode C11 and the second touch/common electrode C21 underlying the first touch/common electrode C11. Namely, the second gate line G2 between the adjacent touch/common electrodes C11 and C21 does not overlap any touch/common electrode.
Referring to FIG. 5, when gate signals are sequentially supplied to the first to third gate lines G1 to G3, a ripple voltage is generated at a start point “a” and an end point “b” of each gate signal due to a coupling signal between the gate signal and the common voltage. However, a defective image is displayed on horizontal lines in the related art touch sensor integrated type display device because of a difference between a first parasitic capacitance between a gate line inside a touch/common electrode and the touch/common electrode, and a second parasitic capacitance between a gate line at a boundary of vertically adjacent touch/common electrodes and the touch/common electrode.
More specifically, for example, a first ripple voltage r1 is generated in a touch/common electrode CI 1 of a proceeding stage by a first gate signal supplied to a first gate line G1 inside the touch/common electrode C11. When a second gate signal subsequent to the first gate signal is supplied to a second gate line G2, a second ripple voltage r2 having the same amplitude as the first ripple voltage r1 and a polarity opposite the first ripple voltage r1 is generated in the touch/common electrode C11 by the second gate signal. Thus, in the touch/common electrode C11 of the proceeding stage, the first ripple voltage r1 can be compensated by the second ripple voltage r2 having the same amplitude and the same frequency as the first ripple voltage r1.
However, a third ripple voltage r3 having the same configuration as the first ripple voltage r1 is generated at a boundary of the touch/common electrode C11 of the proceeding stage adjacent to the second gate line G2 by the second gate signal supplied to the second gate line G2 related to pixel electrodes P corresponding to the touch/common electrode C11. Further, a fourth ripple voltage r4 having an amplitude smaller than the third ripple voltage r3 is generated at a boundary of a touch/common electrode C21 of a subsequent stage adjacent to the second gate line G2 because there is an open area between the first touch/common electrode C11 and the second touch/common electrode C21. As a result, the fourth ripple voltage r4 cannot compensate for the third ripple voltage r3.
Accordingly, in the related art touch sensor integrated type display device, a level of the common voltage becomes unstable because of a difference between a first ripple voltage difference V1 inside the touch/common electrode and a second ripple voltage difference V2 at a boundary of the touch/common electrode. Hence, when the pixels are charged, bright horizontal lines are displayed on an image due to changes in the level of the common voltage, thereby generating a defective image.